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Specific hopanoid classes differentially affect free-living and symbiotic states of Bradyrhizobium diazoefficiens.

Kulkarni G, Busset N, Molinaro A, Gargani D, Chaintreuil C, Silipo A, Giraud E, Newman DK - MBio (2015)

Bottom Line: These defects might be due to a less rigid membrane resulting from the absence of free or lipidA-bound C35 hopanoids or the accumulation of the C30 hopanoid diploptene.Our results also show that C35 hopanoids are necessary for symbiosis only with the host Aeschynomene afraspera but not with soybean.Moreover, this work has geobiological relevance: hopanes, molecular fossils of hopanoids, are enriched in ancient sedimentary rocks at discrete intervals in Earth history.

View Article: PubMed Central - PubMed

Affiliation: Division of Biology and Biological Engineering, California Institute of Technology, Pasadena, California, USA.

No MeSH data available.


Related in: MedlinePlus

Growth of B. diazoefficiens strains under various stress conditions. (A to D) Growth of the WT (circles), the ΔhpnP mutant (squares), and the ΔhpnH mutant (triangles) was monitored as optical density at 600 nm (OD600) in PSY at 30°C (A), PSY at 37°C (B), microaerobic PSY with 0.5% O2 at 30°C (C), and PSY at pH 6 and 30°C (D). Each curve represents the average of at least three biological replicates, except the microaerobic growth curves, for which a representative data set out of four trials is shown. (E and F) Growth of B. diazoefficiens strains under stress as measured in stressor gradient plates with 50 mM NaCl, 500 mM inositol, 0.4% bile salts, or 1 mM EDTA (E) or by disc diffusion assays with 10% SDS, 5.5 M H2O2, and 2 M HCl (F). Error bars represent standard errors (n = 9). *, P < 0.05, and **, P < 0.01, by Tukey’s honestly significant difference test. (G) NCR335 sensitivity of B. diazoefficiens strains.
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fig4: Growth of B. diazoefficiens strains under various stress conditions. (A to D) Growth of the WT (circles), the ΔhpnP mutant (squares), and the ΔhpnH mutant (triangles) was monitored as optical density at 600 nm (OD600) in PSY at 30°C (A), PSY at 37°C (B), microaerobic PSY with 0.5% O2 at 30°C (C), and PSY at pH 6 and 30°C (D). Each curve represents the average of at least three biological replicates, except the microaerobic growth curves, for which a representative data set out of four trials is shown. (E and F) Growth of B. diazoefficiens strains under stress as measured in stressor gradient plates with 50 mM NaCl, 500 mM inositol, 0.4% bile salts, or 1 mM EDTA (E) or by disc diffusion assays with 10% SDS, 5.5 M H2O2, and 2 M HCl (F). Error bars represent standard errors (n = 9). *, P < 0.05, and **, P < 0.01, by Tukey’s honestly significant difference test. (G) NCR335 sensitivity of B. diazoefficiens strains.

Mentions: Does a less rigid membrane affect the fitness of ΔhpnH at different temperatures? To address this question, we compared aerobic growth rates of the ΔhpnH mutant at 30°C and 37°C with those of the WT and the ΔhpnP mutant (Fig. 4A and B). The ΔhpnP mutant grows like the WT at both temperatures, whereas the ΔhpnH mutant grows slower at 30°C and is unable to grow at 37°C. These results suggest that C35 hopanoids are important for growth at ambient temperature (30°C) and essential for growth at higher temperature (37°C). As shown in our whole-cell membrane fluidity measurements, the higher the temperature, the less rigid the membrane. This might be the reason why C35 hopanoids are absolutely required to maintain membrane rigidity at 37°C but are dispensable at 30°C. It is important to note that the phenotypic defect of the ΔhpnH mutant could be due to either the absence of C35 hopanoids or the lack of downstream products, such as HoLA, and even accumulation of the HpnH substrate diploptene, or a combination of these factors.


Specific hopanoid classes differentially affect free-living and symbiotic states of Bradyrhizobium diazoefficiens.

Kulkarni G, Busset N, Molinaro A, Gargani D, Chaintreuil C, Silipo A, Giraud E, Newman DK - MBio (2015)

Growth of B. diazoefficiens strains under various stress conditions. (A to D) Growth of the WT (circles), the ΔhpnP mutant (squares), and the ΔhpnH mutant (triangles) was monitored as optical density at 600 nm (OD600) in PSY at 30°C (A), PSY at 37°C (B), microaerobic PSY with 0.5% O2 at 30°C (C), and PSY at pH 6 and 30°C (D). Each curve represents the average of at least three biological replicates, except the microaerobic growth curves, for which a representative data set out of four trials is shown. (E and F) Growth of B. diazoefficiens strains under stress as measured in stressor gradient plates with 50 mM NaCl, 500 mM inositol, 0.4% bile salts, or 1 mM EDTA (E) or by disc diffusion assays with 10% SDS, 5.5 M H2O2, and 2 M HCl (F). Error bars represent standard errors (n = 9). *, P < 0.05, and **, P < 0.01, by Tukey’s honestly significant difference test. (G) NCR335 sensitivity of B. diazoefficiens strains.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4620461&req=5

fig4: Growth of B. diazoefficiens strains under various stress conditions. (A to D) Growth of the WT (circles), the ΔhpnP mutant (squares), and the ΔhpnH mutant (triangles) was monitored as optical density at 600 nm (OD600) in PSY at 30°C (A), PSY at 37°C (B), microaerobic PSY with 0.5% O2 at 30°C (C), and PSY at pH 6 and 30°C (D). Each curve represents the average of at least three biological replicates, except the microaerobic growth curves, for which a representative data set out of four trials is shown. (E and F) Growth of B. diazoefficiens strains under stress as measured in stressor gradient plates with 50 mM NaCl, 500 mM inositol, 0.4% bile salts, or 1 mM EDTA (E) or by disc diffusion assays with 10% SDS, 5.5 M H2O2, and 2 M HCl (F). Error bars represent standard errors (n = 9). *, P < 0.05, and **, P < 0.01, by Tukey’s honestly significant difference test. (G) NCR335 sensitivity of B. diazoefficiens strains.
Mentions: Does a less rigid membrane affect the fitness of ΔhpnH at different temperatures? To address this question, we compared aerobic growth rates of the ΔhpnH mutant at 30°C and 37°C with those of the WT and the ΔhpnP mutant (Fig. 4A and B). The ΔhpnP mutant grows like the WT at both temperatures, whereas the ΔhpnH mutant grows slower at 30°C and is unable to grow at 37°C. These results suggest that C35 hopanoids are important for growth at ambient temperature (30°C) and essential for growth at higher temperature (37°C). As shown in our whole-cell membrane fluidity measurements, the higher the temperature, the less rigid the membrane. This might be the reason why C35 hopanoids are absolutely required to maintain membrane rigidity at 37°C but are dispensable at 30°C. It is important to note that the phenotypic defect of the ΔhpnH mutant could be due to either the absence of C35 hopanoids or the lack of downstream products, such as HoLA, and even accumulation of the HpnH substrate diploptene, or a combination of these factors.

Bottom Line: These defects might be due to a less rigid membrane resulting from the absence of free or lipidA-bound C35 hopanoids or the accumulation of the C30 hopanoid diploptene.Our results also show that C35 hopanoids are necessary for symbiosis only with the host Aeschynomene afraspera but not with soybean.Moreover, this work has geobiological relevance: hopanes, molecular fossils of hopanoids, are enriched in ancient sedimentary rocks at discrete intervals in Earth history.

View Article: PubMed Central - PubMed

Affiliation: Division of Biology and Biological Engineering, California Institute of Technology, Pasadena, California, USA.

No MeSH data available.


Related in: MedlinePlus